Progressive macular hypomelanosis of the trunk: primary acquired hypopigmentation.

Dermatological practice in Martinique frequently encounters a bizarre skin condition presenting as a progressive and extensive hypomelanosis on the back. The course of this disorder is highly characteristic: it occurs mainly in females from 18-25 years of age, with a progressive development of round, pale, coalescent macules on the back and sometimes on the abdomen. This disease, which does not respond to therapy, spontaneously regresses within 3 to 4 years. Decreased epidermal melanin is the only histological feature. Ultrastructural examination of two cases found that the macular lesions were characterized by a switch from Stage IV single melanosomes (negroid) to small Type I-III aggregated melanosomes (caucasoid). It may thus be stated that the variation in skin coloration in these patients was due to a variation in melanosome size and distribution.